1. Field of the Invention
The present invention relates digital multimedia broadcast, and more particularly to a digital broadcast transmission/reception apparatus with rapid channel change through reduction of the parsing time for program specific information (PSI).
2. Description of the Related Art
An analog television displays a corresponding broadcast of a channel when a physical channel change occurs, but a digital television requires a delay of at least two seconds until it displays a corresponding broadcast of a channel when a physical channel change occurs. Such a time delay in a channel change is regarded as a weak point of digital broadcasting, as compared with analog broadcasting.
This delay time in the digital television is the sum of channel tuning time, PSI parsing time, and Audio/Video (A/V) decoding time. The first factor “channel tuning time” is determined according to the tuning speed of a physical tuner, the second factor “parsing time” is determined according to a parsing algorithm, and the third factor “A/V decoding time” is determined according to the setup of a physical buffer Video Buffering Verifier (VBV) and I(Intra)-frame detection.
FIG. 1 is a block diagram illustrating the construction of a PSI parsing unit in a conventional digital broadcasting reception apparatus.
According to the conventional digital broadcasting reception apparatus, the PSI parsing unit 100 extracts a Program Association Table (PAT) 103 and a Program Map Table (PMT 105) by demultiplexing a digital broadcast received through a tuner 101, and transmits a relevant elementary stream (ES) to a decoder 107, thereby providing a digital broadcast to the user.
In more detail, the PSI parsing unit 100 first extracts the PAT 103 through a first demultiplexer 102, and demultiplexes the output of the first demultiplexer 102 in a second demultiplexer 104 using the information of the PAT 103, thereby extracting the PMT 105. Then, the PSI parsing unit 100 extracts an elementary stream (ES) in a third demultiplexer 106 using the PMT 105. Such PSI parsing causes a time delay upon a channel change, so research is being conducted to reduce such a PSI parsing time.
Generally, in a digital television, when a physical channel change occurs, PAT parsing, PMT parsing, and filtering procedures are sequentially performed before a corresponding digital broadcast is displayed. This means that a channel change time is extended. Various methods have been proposed in order to reduce the PSI parsing time. However, it is not easy to apply such methods due to several reasons; for example, these methods may require additional hardware.
There has been proposed a method for improving a channel change speed in a digital broadcasting receiver (set-top box), in which a tuner is additionally installed in a reception terminal so as to scan all channels and to store PSI obtained through the scanning in a memory. However, this method has a problem in that a separate tuner must be installed in the reception terminal. Another proposed method for removing the searching time for a PSI packet in digital multimedia broadcasting (DMB), in which a transport stream (TS) is buffered in a reception terminal during about two seconds, and then a PAT and a PMT included in the buffered data are parsed, thereby reducing a delay time. However, since this method unnecessarily buffers the stream in the reception terminal during two seconds, a longer time delay may be incurred, as compared with a general algorithm which parses PSI without such a buffering process.
Third, there has been proposed a method for reducing an initial starting time of a DMB terminal through PMT search, in which a search is performed in order to find a TS whose header and payload includes predetermined bits identical to those of a PMT. Although this method may have an effect in a single channel for PMT, this method requires longer waiting time and PAT parsing time for all channels under a multi-channel environment.